This invention relates in part to the use of RNA interference (RNAi) technology in cancer cells to knock out genes encoding DNA replication proteins, resulting in cell cycle arrest, and cytotoxicity. RNAi technology enables specific suppression of the expression of virtually any gene and provides a new tool for drug target discovery, validation, and therapy. To obtain functional RNAi reagents for biological, biomedical, and clinical applications, it is important to identify potent interfering RNA molecules (RNAi molecules) for a gene of interest.
Cancer is the second leading cause of death in industrialized countries, resulting from a combination of mutations in certain oncogenes and tumor suppressor genes. Cancer can arise due to deregulation at many points of the cell cycle and during cell differentiation. Cell cycle checkpoints are a critical mechanism for assessing DNA damage. When damage is found, the checkpoint either arrests the cell cycle until the damage is repaired or targets the cell for destruction via apoptosis if repairs cannot be made.
Chromosomal translocations involving the MLL gene on chromosome 11q23 are found in about 10% of all human leukemias and define one of the most adverse genetic markers associated with chemotherapy resistance and poor prognosis. MLL is a H3K4 methyltransferase that acts as transcriptional master regulator in normal hematopoiesis. Fusion proteins resulting from 11q23 translocations are thought to misdirect transcriptional activation, reestablish self-renewal capacity and thereby promote leukemogenesis. Various MLL cofactors, as well as downstream target genes, have been shown to be involved in MLL-leukemogenesis and have been proposed as targets for therapeutic intervention.